Bluetooth wideband scan mode

ABSTRACT

Different scan modes are provided for Bluetooth devices. In at least some embodiments, a narrowband scanning mode looks for signal energy on individual transmission frequencies at a time. By looking for signal energy rather than decoding transmitted packets, at least some of the components in a Bluetooth device can remain in an idle or rest state. A midband scanning mode looks for signal energy across multiple different frequencies at a time. Again, by looking for signal energy across multiple different frequencies rather than decoding transmitted packets, at least some of the components in a Bluetooth device can remain in an idle or rest state. A wideband scanning mode looks for signal energies across all relevant frequencies at a time. At least some embodiments enable a Bluetooth device to switch between scanning modes.

RELATED APPLICATION

This application claims priority to U.S. Utility application Ser. No.12/190,251, filed on Aug. 12, 2008 which in turn claims priority to U.S.Provisional Application No. 60/955,497, filed on Aug. 13, 2007, thedisclosure of which is incorporated by reference herein.

BACKGROUND

Bluetooth technology allows Bluetooth devices to discover one anotherwhen they are within range and then to connect to one another. Discoveryand subsequent connection to another Bluetooth device occurs throughinquiry and page scan operations. The purpose of the inquiry operationis to discover other Bluetooth devices; and, the purpose of the pagescan operation is to connect to other Bluetooth devices.

In operation, a first Bluetooth device, termed a “master”, acts as aninquirer by transmitting short packets at a very fast rate. A seconddevice, termed a “slave”, listens for those packets by conducting aninquiry scan at a much slower rate. During this process, channel hoppingis employed, as will be appreciated by the skilled artisan, so thateventually the devices will synchronize up with one another.

One of the problems associated with the discovery process is that duringthe time when the slave device listens for packets in its inquiry scan,the slave device is in a full receive state or mode, meaning thatcurrent draw and power consumption are high. This problem can beparticularly challenging in the context of battery-powered devices.

SUMMARY

This Summary is provided to introduce subject matter that is furtherdescribed below in the Detailed Description and Drawings. Accordingly,the Summary should not be considered to describe essential features norused to limit the scope of the claimed subject matter.

In one embodiment, a method comprises initiating a wideband scan mode ina Bluetooth slave device, wherein the wideband scan mode is one otherthan a full receive mode; receiving a signal from a Bluetooth masterdevice; ascertaining whether an energy pattern for multiple channelswith respect to the received signal is detected; and if the energypattern is detected, entering the full receive mode.

In another embodiment, a Bluetooth device comprising circuitryconfigured to: initiate a wideband scan mode, wherein the wideband scanmode is one other than a full receive mode; receive a signal from aBluetooth master device; ascertain whether an energy pattern formultiple channels with respect to the received signal is detected; andif the energy pattern is detected, enter the full receive mode.

In another embodiment, a system comprises means for initiating awideband scan mode in a Bluetooth slave device, wherein the widebandscan mode is one other than a full receive mode; means for receiving asignal from a Bluetooth master device; means for ascertaining whether anenergy pattern for multiple channels with respect to the received signalis detected; and means for entering the full receive mode if the energypattern is detected.

BRIEF DESCRIPTION OF THE DRAWINGS

The same numbers are used throughout the drawings to reference likefeatures.

FIG. 1 depicts an example operating environment in accordance with oneor more embodiments.

FIG. 2 illustrates a typical topology of a network of devices that arecommunicatively linked using wireless connections in accordance withBluetooth technology.

FIG. 3 illustrates a block diagram of a Bluetooth device.

FIG. 4 illustrates an example electrical circuit that can be used inaccordance with one or more embodiments.

FIG. 5 is a flow diagram that describes steps in a method in accordancewith one or more embodiments.

FIG. 6 is a diagram that depicts multiple Bluetooth channels inaccordance with one or more embodiments.

FIG. 7 is a flow diagram that describes steps in a method in accordancewith one or more embodiments.

FIG. 8 is a diagram that depicts Bluetooth transmissions in accordancewith one or more embodiments.

FIG. 9 illustrates an electrical circuit that can be used in a widebandmode in accordance with one or more embodiments.

FIG. 10 is a flow diagram that describes steps in a method in accordancewith one or more embodiments.

FIG. 11 is a flow diagram that describes steps in a method in accordancewith one or more embodiments.

DETAILED DESCRIPTION

Overview

In various embodiments, different scan modes are provided for Bluetoothdevices. In at least some embodiments, a narrowband scanning mode isemployed that looks for signal energy on individual transmissionfrequencies at a time. By looking for signal energy rather than decodingtransmitted packets, at least some of the components in a Bluetoothdevice can remain in an idle or rest state. In at least some otherembodiments, a midband scanning mode is employed and looks for signalenergy across multiple different frequencies at a time. By looking forsignal energy across multiple different frequencies rather than decodingtransmitted packets, at least some of the components in a Bluetoothdevice can remain in an idle or rest state. In at least some otherembodiments, a wideband scanning mode is employed and looks for signalenergies across all relevant frequencies at a time. Further, at leastsome embodiments enable a Bluetooth device to switch between scanningmodes as will become apparent below.

In the discussion that follows, a section entitled “OperatingEnvironment” is provided and describes one example operating environmentin which one or more embodiments can be employed. Following this, asection entitled “Narrowband Mode” is provided and describes anembodiment that employs a narrowband scanning mode in a Bluetoothdevice. Following this, a section entitled “Midband Mode” is providedand describes an embodiment that employs a midband scanning mode. Next,a section entitled “Wideband Mode” is provided and describes anembodiment that employs a wideband scanning mode. Following thissection, a section entitled “Switching between Modes” is provided anddescribes embodiments that enable a Bluetooth device to switch betweenvarious scanning modes.

Operating Environment

FIG. 1 depicts an example operating environment in accordance with oneor more embodiments, generally at 100. In this particular example, theoperating environment includes a master device 102 and a slave device104, referred to herein as “Bluetooth devices”. In some instances, theoperating environment can include multiple master devices and multipleslave devices. However, for purposes of simplicity and brevity, only oneof each type of device is shown.

As will be appreciated by the skilled artisan, the master and slavedevices can be embodied as any suitable digital device including, by wayof example and not limitation, telephones, laptop computer systems, headsets, printers, personal digital assistants, desktop computer systems,fax machines, keyboards, joy sticks, and virtually any other type ofdigital device. Typically, such devices include a Bluetooth transceiverto both transmit and receive signals.

In operation, a device discovery process is used by master device 102 todiscover one or more slave devices such as slave device 104. Initially,master device 102 sends or broadcasts a general inquiry message orinquiry that can be received by slave device 104. When the master device102 broadcasts an inquiry, it typically remains in an inquiry state fora predetermined period of time which may be programmable. If a slavedevice, such as slave device 104, is in a discoverable state, the slavedevice enters into an inquiry scan during which time it scans forinquiries for a predetermined period of time. The slave device 104 canthen send an inquiry response to the master device 102. The inquiryresponse can provide information such as a Bluetooth device address forthe master device 102 to use for connecting to the slave device 104.

To connect to a slave device, a master device then sends a page to theslave device that responded to its inquiry. In response to a page, theslave device sends a page response that provides information thatenables the master device to display a user-friendly name for a user toselect for connection to the slave device.

In a normal page scan operation, the master device 102 hops frequenciesat 3200 hops per second over 32 channels. The master device typicallytransmits an ID packet having a duration of 68 μs every 312.5 μs.Typically, the 32 channels are split into two trains of 16 sub-channels.The master device steps through a train in 10 ms and then repeats thetrains in a certain pattern for a programmable duration such as, forexample, 5.12 seconds or 10.24 seconds. The master device operates in arepeated pattern, for example, transmit-transmit-receive-receive patternuntil the slave device responds or times out.

The slave device 104 typically opens a scan window having a duration of11.25 ms every 1.28 seconds, both durations of which are programmable.During this time, the slave device dwells at different channels at everyscan window. The slave device responds once an ID packet has beendetected and follows using the remaining connection set up protocol. Fora 5.12 second master paging duration, there are typically four chancesfor the slave device to detect the ID packet from the master device.

FIG. 2 illustrates a typical topology of a network 200 of devices thatare communicatively linked using wireless connections in accordance withBluetooth technology. In this example, a piconet 202 includes devices206, 208, and 210 that are wirelessly, communicatively linked. Likewise,a piconet 204 includes devices 212, 214, and 216 that are wirelessly,communicatively linked. Further, piconets 202, 204 are wirelessly,communicatively linked by virtue of a link between devices 208 and 212.As noted above, the illustrated devices can comprise any suitable typeof device.

FIG. 3 illustrates a block diagram of a Bluetooth device generally at300. In this example, Bluetooth device 300 includes an RF module 302, alink controller 304, and a microcontroller 306. In addition, an antenna308 is operatively coupled with the RF module 302.

Antenna 308 transmits and receives radio signals that are processed byRF module 302. The RF module comprises a Bluetooth radio which providesvarious functionality including, by way of example and not limitation,bridging to data networks and forming picotnets of connected devices.The Bluetooth radio operates in accordance with the Bluetooth standardBT2.1. Link controller 304 is embodied as a hardware digital signalprocessor for performing, among other processing, various basebandprocessing operations. Microcontroller 306 provides a separate centralprocessing unit for managing the Bluetooth device and for handlinginquiries and requests. The microcontroller can be used to discover andcommunicate with other Bluetooth devices via a Link Manager Protocol orLMP. The Link Manager Protocol provides services including, by way ofexample and not limitation, sending and receiving data, inquiring andreporting names or device identifiers, making and responding to linkaddress inquiries, connection set up, authentication, and link modenegotiation and set up.

Having considered an example operating environment and some backgroundprinciples on Bluetooth operation, consider now a discussion of variouspower-saving scanning modes in accordance with one or more embodiments.

Narrowband Mode

In one or more embodiments, a narrowband scanning mode is utilized tolook for energy on a particular frequency. In at least some embodiments,the narrowband scanning mode does not utilize a full Bluetooth receivestate, and hence full current consumption during the scan period.Instead, a sub-state is entered during which time the Bluetooth devicedoes not attempt to decode a packet. Rather, the Bluetooth device looksfor energy on a frequency and, responsive to finding energy on afrequency that fits a particular profile, a decision is made that acorresponding signal is a legitimate Bluetooth transmission.

With a scanning device, such as a Bluetooth slave device, one typicallywants the device to be discoverable at all times. However, one does notnecessarily know that there is another device, such as a master device,attempting to discover the slave device.

In accordance with one or more embodiments, when an energy detectionscan is conducted, only the transceiver and a couple other componentsare in an operational state. This serves to conserve power and henceconstitutes an operating efficiency. One of the advantages of using anarrowband scan is that the same system architecture can be used for thetransceiver as well as other components on the device. Another of theadvantages of using narrowband scanning is that adverse impacts due tointerference can be reduced. One trade-off, however, is that compared toother scanning modes described below, there can be a higher currentconsumption. In some implementations, the current estimation for currentconsumption in the narrowband embodiment is about 20 milliamps.

FIG. 4 illustrates an example electrical circuit that can be used inaccordance with one or more embodiments generally at 400. The electricalcircuit is incorporated in the receiver portion of a Bluetooth system.In this example, the electrical circuit comprises an antenna 401connected through an amplifier 403 to a mixing/downconverting circuit402 that includes a local oscillator 404 and a mixer 406. In one or moreembodiments, the local oscillator 404 employs a closed loop phase lockloop. The mixing/downconverting circuit 402 is connected through afeedback amplifier 405 to a filter 408. Filter 408 is operably connectedto a peak detector 410 and, through an amplifier 407 toanalog-to-digital converter 414. A second peak detector 412 is providedand receives as input the output of the amplifier connecting filter 408and analog-to-digital converter 414. The output of peak detectors 410,412 is provided to a digital signal processor 416 whose outputconstitutes an interrupt signal that is provided to medium accesscontrol component or MAC 420. The output of analog-to-digital converter414 is provided as input to a main digital signal processor 418.

In operation, a signal is received by the antenna and down converted bymixing/down converting circuit 402 to a frequency of 2 MHz with abandwidth of 1 MHz. The energy of the received signal is detected by thepeak detectors 410, 412 and analyzed by DSP 416. If a duration thresholdthat is set for the energy is reached, then the DSP 416 knows that thesignal constitutes a Bluetooth package and not some other signal such asWIFI or microwave signal. If such is the case, DSP 416 generates aninterrupt signal which is provided to MAC 420 effectively waking the MACand other components up to operate in a normal receive mode in whichpackets can be decoded.

In the illustrated and described embodiment, at least some of thecomponents of electrical circuit 400 are not turned on or operationalduring energy detection operations. These include analog-to-digitalconverter 414, main DSP 418, and MAC 420. Specifically, these componentsdo not need to be continuously on. Rather, they are on for only a shortperiod of time (such as during packet decoding) and are idle otherwise.Most of the time, this circuit operates in a low power mode, by virtueof a number of the components being idle. Only upon an energy detectionmeeting a defined threshold is normal operation assumed.

In operation, the peak detectors are implemented as window thresholddetection circuits. In the particular design, there are two thresholds—ahigh threshold associated with one of the peak detectors, and a lowthreshold associated with the other of the peak detectors. Window peakdetection utilizes both the high and low thresholds. The peak detectorsalso employ a common mode voltage between the high and low thresholds.When a signal is received that crosses the high and low thresholds, thepeak detectors are triggered and a peak will be generated. Based on thispeak generation detected by DSP 416, the interrupt signal is generatedand provided to MAC 420.

Describing this operation from a somewhat higher level, consider thefollowing. The default or normal operation of the scanning or slavedevice is to typically conduct a page and inquiry operationback-to-back, each of which lasts around 11 ms, with a page and inquiryoperation being repeated typically every 1.28 seconds. Normally, thedevice is not necessarily expecting any data at any particular time, butit is ready for data. Each page and inquiry operation constitutes a scanwindow and the time associated with a page and inquiry operation scanwindow is referred to as a scan interval. In the typical Bluetoothdevice, a full receive mode is entered on a scan window during whichtime the device looks for a correlation hit which triggers a response.In the full receive mode, all of the components in FIG. 4 would beoperational. In the illustrated and described embodiment, however,instead of entering a full receive mode on a scan window, a narrowbandscan is performed on a channel that would have been in the normalsequence. In this case, when an energy detection event occurs, asdetected by the peak detectors 410, 412, a normal page scan operation isperformed. The normal page scan operation can be conducted sometimelater because the master device repeats the transmission process for aset period of time, e.g. five seconds, during which time the slavedevice can synchronize to the channel on which transmission occurs.

For example, every 10 ms the master device repeats 16 channels which isgoing to be done 128 times. When an energy detection event occurs on achannel, a full receive mode is conducted to do a full scan. Around 10ms later, the master device should be on the same channel. As will beappreciated by the skilled artisan, Bluetooth employs 79 channels butfor the inquiry and page operations, it uses a subset of 32 channels.For an inquiry operation, the 32 channels are fixed, but for a pageoperation, the 32 channels depend on the master device's Bluetoothaddress. The 32 channels are taken and broken into two trains, eachhaving 16 channels.

In the illustrated and described embodiment, the energy detectionoperation is specific to each channel. In the narrowband mode, theBluetooth baseband notifies the Bluetooth analog radio and the DSP 416on which channel to conduct the narrowband detection operation. Ifenergy is detected on a particular channel, the Bluetooth baseband willinitiate a full receive mode on that channel using MAC 420 and the othercomponents that were idle. During every scan interval, the scanning orslave device changes its channel, but it does this very slowly, e.g.every 1.28 seconds. At same time, the master device transmits on thesechannels very quickly. Thus, the master device repeats transmissionsenough that there is a very good chance that the signals or channelswill line up on both devices.

FIG. 5 is a flow diagram that describes steps in a method in accordancewith one or more embodiments. The method can be performed in connectionwith any suitable hardware, software, firmware, or combination thereof.In one or more embodiments, the method is performed by asuitably-configured Bluetooth slave device.

Step 500 initiates a narrowband scanning mode. An example of anarrowband scanning mode is provided above. Step 502 receives a signalfrom a master device. Step 504 ascertains whether the signal energy withrespect to the received signal meets a defined threshold. The step isperformed in the narrowband scanning mode on a channel by channel basis.If the received signal on a particular channel does not meet the energythreshold, the method returns to 502. If, on the other hand, thereceived signal on the particular channel does meet the energythreshold, step 506 enters a full receive mode. In the illustrated anddescribed embodiment, when a full receive mode is entered, an interruptsignal is generated to wake up components that were otherwise in an idlestate on the slave device. In the example above, components that areawakened include, by way of example and not limitation, MAC 420, mainDSP 418, and analog-to-digital converter 414 (FIG. 4).

Midband Mode

In one or more embodiments, a midband scanning mode can be employed tolisten to multiple channels at a time rather than to a single channel ata time, as in the narrowband mode. Any suitable number of channels canbe used in the midband scanning mode. In the example below, fivechannels are used at a time. It is to be appreciated and understood thatany number of multiple channels can be used without departing from thespirit and scope of the claimed subject matter.

As an example, consider the following in connection with FIG. 6. Assumethe normal 79 Bluetooth channels as shown. In the normal receive mode,the Bluetooth slave device typically remains in one channel for 1.28seconds and then changes to the next channel. During this time, themaster device hops through these channel sequences at a much fasterrate. Accordingly, if the slave device remains at one channel for aperiod of time, the master device is going to hop through the channelsvery quickly and the slave should be able to detect a transmission onthe one channel. In the present embodiment, the bandwidth is opened to 5MHz so that the slave device performs an energy detection on fivechannels at a time. So, if the effective listening channel rangesbetween channels 5-10, as in the Figure, if the master device hops toany of these channels, the slave device should be able to detect this.In this particular example, the circuit of FIG. 4 can be employed with aslight modification. Specifically, instead of using a closed loop phaselock loop in the local oscillator 404, an open loop phase lock loop isemployed.

FIG. 7 is a flow diagram that describes steps in a method in accordancewith one or more embodiments. The method can be performed in connectionwith any suitable hardware, software, firmware, or combination thereof.In one or more embodiments, the method is performed by asuitably-configured Bluetooth slave device.

Step 700 initiates a midband scanning mode. An example of a midbandscanning mode is provided above. Step 702 receives a signal from amaster device. Step 704 ascertains whether a signal energy for multiplechannels with respect to the received signal meets a defined threshold.The step is performed in the midband scanning mode on a multiple channelby multiple channel basis. As noted above, any suitable number ofmultiple channels can be used. If the received signal on a collection ofchannels does not meet the energy threshold, the method returns to 702.If, on the other hand, the received signal on the multiple channels doesmeet the energy threshold, step 706 enters a full receive mode. In theillustrated and described embodiment, when a full receive mode isentered, an interrupt signal is generated to wake up components thatwere otherwise in an idle state on the slave device. In the exampleabove, components that are awakened include, by way of example and notlimitation, MAC 22, main DSP 24, and analog-to-digital converter 26(FIG. 4).

Wideband Mode

In one or more embodiments, a wideband scanning mode can be employed tolisten to all of the channels simultaneously rather than to individualchannels or a sub-set of channels, as in the narrowband and midbandscanning modes respectively.

One of the challenges of using the wideband scanning mode stems fromnoise that might be present within the range of channels which cannot bedifferentiated in terms of the channel or channels on which the noiseoccurs. An advantage of the wideband scanning mode, however, is that thepattern created by an inquiring or paging device (i.e. master device) isvery distinct and very repetitive and is going to repeat multiple timesin the period of one of the scan windows. So, in this case, the slavedevice looks for energy with a pattern that is distinct rather than aspike, as in the narrowband scanning mode.

As an example, consider FIG. 8. Typically, as shown at 800, theinquiring or master device transmits first at T1 on a first channel andthen transmits again at T2 on a second different channel. It thenlistens for a response as indicated by R1 and R2. R1 and R2 correspondto the same channel on which the transmissions occur, e.g. T1 and T2respectively. The master device typically performs this operationrepeatedly for a pre-determined period of time—e.g., for a minimum offive seconds. In the period of a scan window on the slave device, thereare going to be 16 transmits on 16 different frequencies.

In the illustrated and described embodiment, the slave device employs afilter that looks for this particular pattern and it provides a basebandindication of how closely a match the energy of the receivedtransmission is to this pattern. When a match occurs, a full scan istriggered and the slave device enters a full receive mode, as in theabove example.

One advantage of this approach is that because the pattern is repeating,it is unique. Specifically, in at least some embodiments, thetransmission pattern can be characterized by a profile that is a regularand recognizable profile. For example, each transmission, e.g. T1 andT2, lasts for 68 μs and there is a separation of 312.5 μs. Accordingly,the slave device looks for this pattern, as indicated at 802.Accordingly, the slave device attempts to detect energy that fits thispattern in terms of a qualified width of the energy (e.g., 68 μs) with aseparation of 312.5 μs between energy detections, over a period of timethat includes multiple transmissions on the same frequency.

Thus, in this example, if the slave device looks at a window of 1250 μs,the above pattern is going to repeat over and over. If the slave deviceis in a clean environment, which is to say an environment that is freefrom noise, the slave device should detect the precisely-transmittedwaveform in terms of its energy. If, however, there is some noise in theenvironment such as that caused by other devices, the slave device willsee this noise as indicated by the dashed lines in 802. In operation,data transmission information is collected over a programmable periodtime, such as either during a full frame or a portion of a frame, suchas half of a frame. Over time, during the master device's multipletransmissions, the slave device can build a histogram such as that shownat 804. For example, in at least some embodiments, to construct ahistogram over the 1250 μs, multiple samples are taken every 32 μs. Eachsample is stored into a memory element or accumulator. For the next 1250μs, samples are taken and stored back into the accumulator to correspondto the previous samples at locations in the previous 1250 μs window.

The illustrated histogram constitutes a clean histogram in a cleanenvironment. However, if there is interference or noise, the histogrammay contain noise data, such as that shown by the dashed line labeled“Noise”. In one or more embodiments, to deal with the noise issue,different thresholds can be programmed and set to look for energy peaksin the histogram, the width of the peaks and the distance between thepeaks, such as 68 μs and 312.5 μs, respectively. For example, a firstthreshold such as Threshold 1 can be set to look for energy peaks, and asecond threshold such as Threshold 2 can be set to recognize noise.Based on this programmability in terms of threshold setting, if there isa close match of the pattern that is being looked for, the slave devicecan conclude that this is a desirable pattern that corresponds to amaster device making an inquiry. From this information, the slave devicecan generate an interrupt signal to the overall system which wakes upidling components. Responsively, the slave device can then decode thenext transmitted packet and ascertain whether a response is to be sentto the master device. In at least some embodiments, if there is somenoise in the histogram, then the slave device may enter a differentscanning mode, such as the narrowband or midband scanning modes to dealmore appropriately with the noise, as described below.

Programmability provides an opportunity to look at a programmable numberof iterations. Accordingly, the slave device can look for patterns thatare repeated a number of times and make a decision to generate aninterrupt signal based on a recognized pattern. Alternately oradditionally, if the slave device is a clean environment, the scanwindow can be shrunk and then any indication of energy can be used to gointo a regular scan or receive mode. This provides the ability foraggressive power management in clean environments. That is, as the slavedevice encounters a noisy environment, through programmability, thelength of the scan window can be increased as well as the patternrequirements adapted to suit the environment.

FIG. 9 illustrates an electrical circuit that can be used in thewideband mode in accordance with one or more embodiments. In thisexample, the circuit is similar to that shown in FIG. 4. Accordingly,for the sake of brevity, like components use like numerals and thedescription of such components is not repeated here. In the widebandimplementation, an open loop voltage controlled oscillator or VCO isused for local oscillator 404. In the wideband mode, filter 408 isshutoff and bypassed by a bypass 900 as shown. In this case, peakdetector 412 is used for energy detection. In this case, instead ofsetting the local oscillator frequency to either upper or lower valuesof the channels, the oscillator frequency is set to mid-channel. Settingthe frequency to mid-channel enables 80 MHz to be captured collectivelywith 40 MHz on each side of the frequency setting. In terms of powersavings, there is an advantage at the system level because previously,in the narrowband and midband modes, the MAC 420 or Bluetooth basebandwould wake up, calculate the channel, and then perform timing operationsas will be appreciated by the skilled artisan. In this system, however,since the channel is not programmed, the MAC 420 does not have to wakeup to program any channels during energy detection.

FIG. 10 is a flow diagram that describes steps in a method in accordancewith one or more embodiments. The method can be performed in connectionwith any suitable hardware, software, firmware, or combination thereof.In one or more embodiments, the method is performed by asuitably-configured Bluetooth slave device.

Step 1000 initiates a wideband scanning mode. An example of a widebandscanning mode is provided above. Step 1002 receives a signal from amaster device. Step 1004 ascertains whether an energy pattern formultiple channels with respect to the received signal is detected. Thestep can be performed by building a histogram over the receivedtransmissions and then ascertaining from the histogram whether theenergy pattern is detected. As noted above, one or more thresholds canbe set to look for not only the desired energy pattern, but for noise aswell. If the energy pattern is not detected, the method returns to 1002.If, on the other hand, the energy pattern is detected, step 1006 entersa full receive mode. In the illustrated and described embodiment, when afull receive mode is entered, an interrupt signal is generated to wakeup components that were otherwise in an idle state on the slave device.In the example above, components that are awakened include, by way ofexample and not limitation, MAC 420, main DSP 418, and analog-to-digitalconverter 414 (FIG. 4).

Switching Between Modes

As noted above, in at least some embodiments, the slave device isconfigured to switch between different scanning modes.

In one or more embodiments, the slave device initiates operation in itslowest power mode—here, the wideband scanning mode. The slave deviceperforms wideband detection at pre-determined intervals which can besustained for an indefinite period of time. Eventually, another devicemay be within the slave device's reception area and begin transmissionsat which time the slave device will see some type of energy detection.When this happens, in at least some embodiments, the slave device maywish to enter into another scanning mode to ascertain whether thetransmissions are from another Bluetooth device or whether thetransmission constitute some type of noise.

In the simplest case, the slave device can enter, from the widebandscanning mode, a regular scanning mode. Thus, when an energy pattern isdetected, a programmable period of regular scanning can be started. Forexample, the slave device might perform four regular scans as four scanscorrespond to the typical length of an inquiry or a page from the masterdevice. During a regular scan, the MAC or Bluetooth baseband will wakeup and perform a scan during the programmable period. When this iscompleted, the slave device will have either found a desirable signal ornot. If it does not find a desirable signal, these components can goidle and the wideband mode can be entered. In addition, a falsedetection can be noted and stored. Specifically, in some embodiments, acounter can keep track of the number of false detections. If the falsedetections reach a particular threshold, the system can fall back into adifferent mode, such as narrowband scanning mode, in which the slavedevice attempts to qualify whether a transmission is really a Bluetoothdevice by narrowing down onto one or more channels. If there is anenergy detection in this mode, the slave device can enter into a regularscan mode. If, in the regular scan mode, nothing is detected, a falsedetection can be noted.

In one or more embodiments, in order to conserve power, one goal is toremain in the wideband scanning mode as long as possible. When an energydetection occurs, the slave device falls back into a different scanningmode, such as a narrowband, midband or regular scanning mode to attemptto scope down on the signal for a set period of time. This can beadvantageous for the following reason. Assume that the slave device isin a noisy environment where the wideband mode would be triggeringregularly. In a worst case scenario, the slave device would switch intoa regular scanning mode, although other modes are possible.

In at least some embodiments, however, the slave device can keep trackthe type of energy detection that occurs. For example, if the energydetection is a strong detection, then the slave device might switch intoa regular scanning mode. If, on the other hand, the energy detection isa weak detection, the slave device might switch into the narrowband ormidband modes.

FIG. 11 is a flow diagram that describes steps in a method in accordancewith one or more embodiments. The method can be performed in connectionwith any suitable hardware, software, firmware, or combination thereof.In one or more embodiments, the method is performed by asuitably-configured Bluetooth slave device.

Step 1100 enters a first scanning mode. Any suitable scanning mode canbe entered. For example, in the illustration above, the first scanningmode constitutes a wideband scanning mode. An example of a widebandscanning mode is provided above. Step 1102 receives a signal from amaster device. Step 1104 ascertains whether an energy profile isdetected. The energy profile can be a profile associated with one ormultiple channels. For example, an energy profile can be associated witha single channel (as in the narrowband scanning mode) or multiplechannels (as in the midband or wideband scanning modes).

If the energy profile is not detected, the method returns to 1102. If,on the other hand, the energy profile is detected, step 1106 enters adifferent scanning mode. For example, if the first scanning mode is awideband scanning mode, the different scanning mode can be one or moreof a narrowband, midband or regular scanning mode.

CONCLUSION

In various embodiments, different scan modes are provided for Bluetoothdevices. In at least some embodiments, a narrowband scanning mode isemployed that looks for signal energy on individual transmissionfrequencies at a time. By looking for signal energy rather than decodingtransmitted packets, at least some of the components in a Bluetoothdevice can remain in an idle or rest state. In at least some otherembodiments, a midband scanning mode is employed and looks for signalenergy across multiple different frequencies at a time. Again, bylooking for signal energy across multiple different frequencies ratherthan decoding transmitted packets, at least some of the components in aBluetooth device can remain in an idle or rest state. In at least someother embodiments, a wideband scanning mode is employed and looks forsignal energies across all relevant frequencies at a time. Further, atleast some embodiments enable a Bluetooth device to switch betweenscanning modes.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed is:
 1. A method comprising: initiating a wideband scan mode in a Bluetooth slave device, the wideband scan mode configured to scan a Bluetooth frequency band while one or more components of the Bluetooth slave device are not awake, the one or more components including a medium access control (MAC) component; receiving a signal over multiple channels of the Bluetooth frequency band; detecting an energy pattern in the received signal based on a first or a second energy pattern threshold, the first energy pattern threshold configured for detection of a Bluetooth master device and the second energy pattern threshold configured for initiation of another scan mode; and responsive to detecting the energy pattern based on the first energy pattern threshold, waking the MAC component of the Bluetooth slave device and entering a normal receive mode to communicate with the Bluetooth master device; or responsive to detecting the energy pattern based on the second energy pattern threshold, initiating a midband scan mode in the Bluetooth slave device to determine whether the received signal is noise or a transmission from the Bluetooth master device; and responsive to a determination in the midband scan mode that the signal is from the Bluetooth master device, entering the normal receive mode.
 2. The method of claim 1, further comprising building a histogram based on the signal received over the multiple channels and wherein detecting the energy pattern detects one of the energy patterns within the histogram.
 3. The method of claim 1, further comprising, responsive to a determination in the midband scan mode that the signal is not from the Bluetooth master device, returning to the wideband scan mode.
 4. The method of claim 1, wherein a bandwidth of the Bluetooth frequency is approximately 80 MHz and the multiple channels over which the signal is received include one or more Bluetooth communication channels within the Bluetooth frequency band.
 5. The method of claim 1, further comprising generating an interrupt signal that wakes up the one or more components on the Bluetooth slave device to initiate the normal receive mode.
 6. The method of claim 1, wherein packets received from the Bluetooth master are not decoded while in the wideband or midband scan modes.
 7. The method of claim 1, further comprising, responsive to not detecting the Bluetooth master device in the normal receive mode, classifying the detection of the energy pattern as a false detection.
 8. A Bluetooth device comprising circuitry configured to: initiate a wideband scan mode, the wideband scan mode configured to scan a Bluetooth frequency band while one or more components of the Bluetooth device are not awake, the one or more components including a medium access control (MAC) component; receive a signal over multiple channels of the Bluetooth frequency band; detect an energy pattern in the received signal based on a first or a second energy pattern threshold, the first energy pattern threshold configured for detection of a Bluetooth master device and the second energy pattern threshold configured for initiation of another scan mode; and responsive to detecting the energy pattern based on the first energy pattern threshold, wake the MAC component of the Bluetooth device and enter a normal receive mode to communicate with the Bluetooth master device; or responsive to detecting the energy pattern based on the second energy pattern threshold, initiate a midband scan mode to determine whether the received signal is noise or a transmission from the Bluetooth master device; and responsive to a determination in the midband scan mode that the signal is from the Bluetooth master device, enter the normal receive mode.
 9. The Bluetooth device of claim 8, wherein the circuitry is further configured to: build a histogram based on the signal received over the multiple channels; and detect one of the energy patterns within the histogram.
 10. The Bluetooth device of claim 8, wherein the circuitry further comprises a window threshold detection circuit that includes at least two peak detectors to detect the energy pattern.
 11. The Bluetooth device of claim 10, wherein a high threshold of the window threshold detection circuit is associated with a first one of the peak detectors and a low threshold of the window threshold detection circuit is associated with a second one of the peak detectors.
 12. The Bluetooth device of claim 10, wherein the circuitry is further configured to, based on the window threshold detection circuit, wake the Bluetooth device by generating an interrupt signal that wakes the one or more components of the Bluetooth device.
 13. The Bluetooth device of claim 12, wherein the interrupt signal wakes a digital signal processor and an analog-to-digital converter of the Bluetooth device.
 14. The Bluetooth device of claim 8, wherein the midband scan mode scans a frequency band of about 5 MHz and consumes more power than the wideband scan mode.
 15. The Bluetooth device of claim 8, wherein the circuitry comprises an open loop voltage controlled oscillator configured to receive the signal over the multiple channels of the Bluetooth frequency.
 16. One or more computer-readable hardware devices comprising processor-executable instructions that, responsive to execution by a processor, cause a Bluetooth device to: initiate a wideband scan mode of the Bluetooth device, the wideband scan mode configured to scan a Bluetooth frequency band while a medium access control (MAC) component of the Bluetooth device is not awake; receive a signal over multiple channels of the Bluetooth frequency band; detect an energy pattern in the received signal based on a first or a second energy pattern threshold, the first energy pattern threshold configured for detection of a Bluetooth master device and the second energy pattern threshold configured for initiation of another scan mode; and responsive to detecting the energy pattern based on the first energy pattern threshold, wake the MAC component of the Bluetooth device and enter a normal receive mode to communicate with the Bluetooth master device; or responsive to detecting the energy pattern based on the second energy pattern threshold, initiate a narrowband scan mode of the Bluetooth device to determine whether the received signal is noise or a transmission from the Bluetooth master device; and responsive to a determination in the narrowband scan mode that the signal is from the Bluetooth master device, enter the normal receive mode to communicate with the Bluetooth master device.
 17. The one or more computer-readable hardware devices of claim 16, wherein a digital signal processor and an analog-to-digital converter of the Bluetooth device are not awake while in the wideband scan mode.
 18. The one or more computer-readable hardware devices of claim 17 comprising additional processor-executable instructions that, responsive to execution by the processor, cause the Bluetooth-enabled device to wake the digital signal processor in response to initiation of the narrowband scan mode.
 19. The one or more computer-readable hardware devices of claim 16 comprising additional processor-executable instructions that, responsive to execution by the processor, cause the Bluetooth-enabled device to return to the wideband scan mode in response to a determination in the narrowband scan mode that the signal is not from the Bluetooth master device.
 20. The one or more computer-readable hardware devices of claim 16, wherein the narrowband scan mode scans a frequency band of about 1 MHz and consumes more power than the wideband scan mode. 